A simple readout circuit has been developed to discriminate the pulse shape from different scintillation crystals in a phoswich-based PET detector as well as measure event energy. As opposed to other methods, this approach only requires a single channel, single ADC with power efficient components. To test this concept, a phoswich PET detector comprising two 3×3×10 mm3 fast and slow LSO crystals (τ d = 34.39 ns and 43.07 ns respectively), side-coupled to a 1×2 array of 6×6 mm2 SensL J-series SiPMs was used. Experimental results verify that the small difference in decay times of the crystals leads to a difference in their integration times to the maximum integrated values. This validates a pulse shape discrimination with 98% of accuracy and a M = 2.33 FOM.